1. Field of the Invention
The present invention relates to a method of and an apparatus for receiving concentrated calls at a terminal of an ATM (asynchronous transfer mode) network.
In a communication network such as a telephone, data, packet, frame-relay, or ATM network, a specific terminal or an area may concentratedly receive calls. For example, a terminal for dealing with mail-order applications, ticket reservations, or answers to questionnaires receives calls concentratedly.
The concentrated calls to such a terminal are restricted by the number of lines, the number of logic channels, available bandwidths, and network resources, so that a caller must repeat a call or must resend a message. The concentrated calls are not only inconvenient for each caller but also troublesome for the terminal to deal with the calls.
2. Description of the Related Art
A communication network usually compels a caller to repeat a call if a terminal to receive the call is busy. If the terminal is a telephone terminal, it will be busy when a line to the terminal is used. If the terminal is an ATM terminal, it will be busy when it has no available bands.
When calls are concentrated to a terminal, the probability of establishing communication with the terminal will be very low even if a caller repeatedly makes a call. In addition, the concentrated calls cause congestion in the exchange that is connected to the terminal and disable the exchange for a given period.
If an exchange in an area is congested due to a disaster in the area or mail-order applications to a specific terminal of the exchange, calls to the subscribers of the exchange are uniformly restricted. If the calls are repeated under this situation, it will aggravate the congestion of the exchange.
If calls are concentrated to a specific terminal in a given period, the terminal will be busy for the period or the network that includes the terminal will be congested for the period, which will disable communication during the period. The congestion will be worsened if the calls are repeated.
If a disaster occurs in an area in a network, the network will be congested. Then, any terminal connected to an exchange in the network will be unable to receive a call.